The study proposes to determine whether sufficient quantities of progenitor cells obtained from umbilical cord blood (CB) can be stratified, genetically engineered to be HIV-resistant, and banked for future use in treating HIV-infected infants. It will evaluate (1) CB cells from mothers stratified for CD4+ cell count for primitive hematopoietic cells and viral burden; (2) the efficiency of retroviral transduction into CB cells; (3) the anti-HIV effect of regulated toxin genes in CB cells; and (4) how freezing and thawing effects CB cells.